miter bar

Yes, I know that some might call this a woodworking problem, some metal.

A few weeks ago I noticed that the miter bar for the miter gauge on my table saw was bent. There was a bow in it of about 3/16 of an inch over a 20 inch length. Its a steel bar, not aluminum, for an Accu-miter gauge.

I know that I've never dropped it or abused it, so I'm wondering how it bent. I find it hard to believe that a 30 degree F temperature variation over the course of some years would do this, and given what it took for me to bend it back, I know that I've never subjected it to that much punishment.

To bend it back, I had to put it in the tail vise on my bench between three pieces of drill rod, then crank down to bend it almost 1/2 inch the other direction. After

4 passes or so at this, I've got the bow down to about 1/16 inch, as measured by a good straightedge.

Since others don't use my shop, any guesses what happened? Stress relief over 10-15 years of use?

Thanks, John

Reply to
John D'Errico
Loading thread data ...

What are the other dimensions of the bar and how is it oriented and mounted?

dennis in nca

Reply to

Hi John,

It could have been an internal stress that just worked its way out over time. If I had to guess, I would suspect that the makers chose cold rolled low carbon steel (1018 or maybe even A36). The stuff is great for welding, has a mill finish good enough to avoid any further machining, and it's pretty cheap. But, cold working the steel produces a great deal of internal stress. A good ME or Machinist knows to stay away from it for anything that needs to be dimensionally stable. Better to use hot rolled steel because it ends up being a lot more stable. Some (like myself) would refer to this as a "design defect" because a different material should have been spec'ed for the application. Alas, it's likely that the cost of materials outweighed engineering sensibilities.

Or, then again, I could be wrong. Even hot rolled steel can have internal stresses. It's a lot less common than cold rolled steel but it can happen. Stress relieving involves a rather lengthy heat treating process which would probably be out of the budget for such an application.

Bend> Yes, I know that some might call this a woodworking problem,

Reply to

Its 3/8 x 3/4 x 20 (inches)

Mounted to the miter gauge at one end by two screws, one about 2 inches from the end, the other at roughly

4 inches from the end.


Reply to
John D'Errico

I'm starting to think that I know what happened.

When I withdraw it from the t-track on the saw table, the front end is captured in the track by a "washer". This prevents it from lifting during use. But when I take it off the table to use a different tool (like a tenoning jig or a panel cutter) I pull it out towards me.

The gauge itself is moderately heavy - about 11 pounds. So as I pull it out, I tend to lift a bit as I withdraw it. Since the end is still captured in the slot, this means I've been gradually cycling it through hundreds of small bends over the years, ALL in the same direction. This is consistent with the direction of the bow.

This feels like the probable cause to me as I think it over. If so, the solution for the future is simple. Slide it forward first to release the washer from the t-slot, then lift it.

Is stress relief with heat an option? I have Mapp gas or propane. Or do I just buy a new bar?


Reply to
John D'Errico

Stress relief? If you did bend it as you suspect then there is no stress to relieve. Just bend it back. It's not like you are likely to distort the steel. You could heat it to bend it back, but you will likely end up causing more damage to the shape of it than if you just finish bending it back into shape as you have already done. Heat is a great friend of working metal, but if you don't know what you are doing or are not careful, that heat and the associated benefits can turn around on you and all you end up with is an interesting twist on a theme.

From what I've read John, you're trying to make too much of this problem. Just bend it back and carry on.

Reply to
Mike Marlow

Just bend it long as it slides well, thats all there is to it. Not exactly a super critical application. And take the stupid washer off the end....does nothing useful in actual use and as you've discovered it makes it harder to put the miter gauge on and off.


Reply to

, John D'Errico

Yep 3/16 inch bend in a 20 inch length means that somebody bent it. Your description sounds like you found the problem. Personally I would throw that washer away, then you could lift the bar out any time you wanted (unless there are other considerations, since I have never used a saw with a T slot). There is absolutely no reason to consider a new bar (a steel bar isn't going to exhibit any kind of movement from stress, What stress?. The only thing that will make it move is temperature change and you will never detect that and it won't affect anything you do. If the bar now lies flat on your table top, you are good to go. If not give it a few appropriate tap (not against the table) to get it to lie flat within a few mils.

Reply to
George E. Cawthon

And don't forget that either now or later on if it starts to get a little loose, you can peen the edges some to tighten it up so it's workable.

Reply to


Well John, as you know, from your experience of trying to bend back the bar, even dead soft cold rolled low carbon steel is very elastic at room temperature (modulus of elasticity is something like 29*10^6 psi). It seems unlikely to me that the pressure of removing your miter gauge from the slot, even many times over many years, would result in gradually bending the bar as much as you say (50% of the thickness). I would expect the washer to have suffered far more damage - especially since it's considerably thinner and on the short end of the lever. The process you have described would be best referred to as repeated stress and the results would be dependent on the plastic properties of the material.

In spite of opinions to the contrary, I'll stick by my original assessment. Stress relief (not "stress", as others have misstated) is the most likely cause. I base this assessment on many years of metalworking. I can easily understand why someone with little or no experience with CRS might consider it a ludicrous theory. If, like one of the responders, you consider your table saw to be a crude machine which is incapable of anything better than rough work, then just bend it back and don't give it a second thought.

Bend> I'm starting to think that I know what happened.

Reply to

Yes, its true that I may be making too much of it.

I have several goals here. I always like to learn what I did wrong (if indeed I did put the bend in it myself by my own methods of work) so that I can avoid a problem like this in the future. I wanted to gain some understanding of the mechanism of what happened. Fixing it myself, if possible, is a goal, but not a tremendously important one, since I could simply replace the bar for a nominal cost.

Thanks all for your feedback, John

Reply to
John D'Errico


Admirable goals, all of them. Very much in line with the attitude of most of us regular RCM'ers.

Do come back, you hear, Bob

Reply to
Bob Engelhardt

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.